一本正經

The number one; single; a; as soon as; entire; whole; all; a "one" radical in Chinese characters; also used for clarity when spelling out numbers.

Root or trunk of a plant; origin or source of something; basis; capital or principal; classifier for books or periodicals; this; current.

Proper; correct; upright; straight; main; principal; exactly; just; positive (math.); first month of the lunar year.

Sacred texts or classics; to pass through or undergo; warp threads in weaving; longitude; channel in TCM; menstruation; surname.